Electrical tissue coagulation has been found to be a proven means of reducing unwanted tissue volumes in surgical practice. High-frequency (HF) electric current is used for coagulation. Different methods exist for its determination.
EP 1 886 636 A1 discloses such a method. It is based on first applying a constant electrical signal (e.g., a constant voltage) to the tissue to ascertain its initial resistance. This phase can last 2 to 3 seconds, for example, and precedes the actual electrosurgical treatment. Other constant parameters such as constant power, constant current or energy, are stipulated for measuring the initial tissue resistance instead of using a constant voltage. After commencing treatment, the initial tissue resistance, the drop in impedance which then takes place, the impedance minimum and the first rise in impedance, are recorded and analyzed. The values of these variables provide information on the conditions at the electrodes and on the tissue type, as well as the moisture level thereof. Treatment parameters are specified accordingly, for example, in terms of the duration of treatment or the energy to be applied. A reference table is used for this purpose and is stored in a memory. A microcontroller uses the treatment values obtained from the reference table and adopts these as a basis for the subsequent treatment.
Surgical procedures are often time-critical. It is therefore desirable to conclude coagulation processes in the shortest time possible while ensuring high quality and reproducibility.